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How did that happen?

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By the way, there is Dolby Surround Mixing Manual available from Dolby as pdf.

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Better Projection Pays!

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Gordy, if the signal is encoded at equal level but with a 90 degree phase difference, the sound will appear in ALL channels at equal level. The matrix regards such a signal as "mid-field" so the steering is turned off. Addition (or subtraction) of 90 degree phase shifted coherent signals results in a 3dB loss, so all four channels will have identical output levels.

Small point I know but remember, accuracy!

In fact there is no way to get simultaneous left only and right only signals from the matrix (anybody's). Only one channel can be predominant at any one time. So Tim's original post intrigued me because it would be impossible to achieve, even with some kind of error. But he has since admitted there WAS centre, it just wasn't HARD centre. Remember the word, Tim - accuracy!

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Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

I have met Gordy, in fact had lunch with him and I must say I have very high regard for the man. In my opinion he is a skilled, very knowledgable and competent cinema engineer. He is also one hell of a nice guy into the bargain. My comments are intended as lighthearted and friendly and I am sure Gordy takes them that way. If I say something that is not quite correct I would expect Gordy or anyone else to correct me, hopefully also in a lighthearted way.

I guess my references to accuracy are really aimed (subliminaly) at people who experience problems with equipment. Taking just a little time to accurately diagnose (and report) a problem makes finding a solution that much faster and easier. I often read Brad saying something like "please give us more information so we can help you".

I should also mention that Australians (particularly me) tend to have slightly different (possibly even bizarre) sense of humour, compared with those residing on other parts of the planet. It comes from living on the underside of the globe where the earth is above your feet and the sky is below your head. Think about it.

Ray

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But he has since admitted there WAS centre, it just wasn't HARD centre. Remember the word, Tim - accuracy!

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Hi Ray, I thought I did describe it accurately. I've said all along that it sounded like it was coming from L and R, which it did. I didn't say it was coming from L and R.

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In fact there is no way to get simultaneous left only and right only signals from the matrix (anybody's). Only one channel can be predominant at any one time.

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I appreciate everyone's input and expertise on this, really. I think the 70% value Gordon cited for the C and S channels was the key. The mix was out of proportion.

Thanks again!

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Better Projection Pays!

Gordy I assume you are talking about the Cat110 Mono/Stereo optical card. Now that was very early in the piece and not a "real" matrix, more of an interim step, and a poor one at that. It used gain riding rather than addition/subtraction.

BTW the person that e-mailed me about Gordy has e-mailed again to say they were only joking. Sigh. See what I mean about differing senses of humour?

Ray

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I know I saw nothing on Ray's comments to take offense at...particularly since they were not aimed at me!

The backward compatibility thing only goes but so far...the 110/116 days and those tracks if played back on modern decoders will not sound the same as if played back on original equipment. The L and R vs C only ducted a small amount to each other to keep a hard center dialogue.

Now if you mean backward compatibility in the sense that a modern film will "play" on old equipment, then yes it will play but will sound nothing like what they heard in the studio.

Steve

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When you get to be the age of Frank or myself, you don't even hear out to 12 KHz.

(Gone are the days when I heard the ultrasonic detectors used for traffic lights, harmonics from an ultrasonic film cleaner, or the high pitched whine of flyback transformers).

Flying small airplanes, high fader settings, and using a two-cycle rototiller in my garden without ear protection have evidently taken their toll.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Besides, a properly designed matrix in a correctly aligned system can fool probably 95% of a cinema audience into thinking they are listening to a discrete playback. It is only when the system malfunctions or there is an alignment problem that the conjuring trick is revealed.

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Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935